Each of our five West Coast national marine sanctuaries is a jewel unto itself with its own unique character. Each has a distinct set of physical conditions, including climate, daily weather patterns, the lay of the coast and the make-up of the seafloor. These and other factors help define the nature of each sanctuary and set each apart from the others.

But in the restless ocean, driven by wind and storms and powerful currents, no place is truly isolated from another. Each of our sanctuaries is intimately connected not only with the others, but also to the entire coast from Alaska to Baja, California, and to the far reaches of the world ocean.

Our national marine sanctuaries on the West Coast are linked by the California Currenta broad, shallow “river” of ocean water meandering southward along the Pacific Coast. This slow-moving surface current carries some 10-trillion gallons of water per houra flow 55 times greater than the Amazon. Below it, two counter currents, the Davidson Current and a deeper undercurrent, flow north.

Carrying cold, nutrient-rich water southward from the North Pacific, the California Current shapes the nature of the entire west coast, setting the stage for an abundance and diversity of ocean life equaled in only a few other places on Earth.

The current runs strongest in spring and summer, when northwest winds drive it southward and towards the coast. During these times, cold, nutrient-rich water wells to the sunlit surface. There, light and nutrients fuel an explosion of life with clouds of tiny, drifting plants known as phytoplankton that form the base of ocean food webs here. Closer to shore, these same forces spur the growth of towering kelp forests.

When it runs strong, the current carries drifting plants and animals southward from sub-arctic waters. When it slackens in the fall, the surface waters warm and southern species move northward. This ever-shifting mix of species adds to the great diversity of our marine communities in our West Coast national marine sanctuaries.

The current serves as a vast, open highway for whales, birds, fishes, and plankton, which follow it on long migrations in search of food or suitable places to nest, spawn, or give birth. For somesuch as Pacific sardines, northern anchovies, gray whales, Western Gulls and Brandt’s Cormorantsthe boundaries of their lives are largely defined by the boundaries of the California Current.

Vast schools of sardines, anchovies and hake spawn in the warmer, waters around the Channel Islands, then swim north through our other sanctuaries where they find rich pastures of plankton to feed on. The small fishes are joined by giant blue whales and other whales that come to feed on krill and various plankton.

Salmon spawned in streams along the Olympic Coast follow the current north to the Gulf of Alaska and south to Cordell Bank, Gulf of the Farallones, Monterey Bay and the Channel Islands sanctuaries in search of food.

Gray whales traverse the entire coast, passing through all five sanctuaries twice each year as they migrate from Alaska to Baja, California. Meanwhile, pods of transient orcas travel from the Olympic Coast to Monterey Bay and Channel Islands in spring to hunt gray whale calves as they swim north with their mothers.

Elephant seals, sea lions and fur seals roam widely along the coast and far out to sea then return to rookeries in the Channel Islands, Monterey Bay and the Gulf of the Farallones national marine sanctuaries where they give birth to their pups.

A Brown Pelican or Black Storm Petrel appearing along the Olympic Coast may have been hatched and fledged on the Channel Islands. And some 400,000 gulls, cormorants and murres nest in the Gulf of the Farallones then fly far and wide to our other sanctuaries and beyond. Our sanctuaries protect vital habitat for shorebirds and countless species, along the important migration route known as the Pacific Flyway.

The connections extend further still as other species pass through these waters on their way to and from more distant places. Each year, albacore tuna follow currents across the Pacific and back again; Sooty Shearwaters travel here from as far away as New Zealand; and leatherback turtles migrate from Indonesia. Albatrosses breeding on the Northwestern Hawaiian Islands regularly fly back and forth to the Olympic Coast and Northern California national marine sanctuaries to find food for their chicks.

The great currents shaping ocean life recognize no man-made boundaries. No one sanctuary can shelter these wide-ranging ocean wanderers. The lines of our sanctuaries can only mark their passage. But taken together, the influence and protection of our sanctuaries extend far beyond their physical boundaries.

Each sanctuary is distinct from the other, but they’re all part of a larger system connected by wind and water. And as part of this greater system, our national marine sanctuaries help protect not just individual places, but the entire fabric of ocean life along the West Coast.